The invention relates to harmonic suppression systems. In particular, the invention relates to mitigating 3rd harmonic currents electrical power distribution systems.
Harmonics in an electrical distribution system are caused by the types of loads connected to the system. Modern electronic equipment and controls, because they draw current in a non-linear fashion, cause harmonic currents to flow throughout the system. The extra currents may result in overloading or failure of system components.
The prior, but not necessarily relevant, art is exemplified by the following U.S. patents: Stacey et al. U.S. Pat. No. 3,849,677; Kennedy U.S. Pat. No. 3,859,542; Thanawala U.S. Pat. No. 3,881,137; Kiko U.S. Reissue Pat. No. 29,080; Elenga et al. U.S. Pat. No. 4,176,310; Arinobu et al. U.S. Pat. No. 4,819,125; Moon et al. U.S. Pat. No. 4,833,344; Paulsson U.S. Pat. No. 4,922,364; Bergdahl et al. U.S. Pat. No. 4,939,486; Kravitz U.S. Pat. No. 4,961,044; and Gilardi et al. U.S. Pat. No. 5,243,648.
The term xe2x80x9cBlockade(trademark) Technologyxe2x80x9d as used herein means technology which: eliminates the production of harmonics at their source; is completely-passive and therefore cost effective, reliable, and efficient; is easily installed and does not require fuses; can handle any load on the distribution system, and does not require load balancing to be effective; and resists overloading (does not require resizing if more harmonic loads are added).
It is a desideratum of the invention to avoid the animadversions of conventional devices and systems dealing with the aforementioned problem.
The present invention provides in a multiple phase electrical distribution system for supplying power from an AC source to one or more nonlinear loads connected to at least one phase line therein, a device for substantially eliminating currents in a neutral wire, said device comprising: a completely-passive parallel resonant circuit having three passive electrical branches connected in parallel; said first completely-passive parallel resonant circuit is tuned to a third harmonic frequency of a fundamental frequency of said AC source; said three passive electrical branches comprise a first branch consisting of a capacitor, a second branch consisting of a reactor, and a third branch consisting of a resistor; and said completely-passive parallel resonant circuit being electrically connected to said neutral wire.
The present invention also provides an electrical system for supplying power to one or more nonlinear loads connected to at least one phase line of a multiple phase distribution system, comprising: a delta-wye transformer; a completely-passive parallel resonant circuit having three passive electrical branches connected in parallel; said first completely-passive parallel resonant circuit is tuned to a third harmonic frequency of a fundamental frequency of said AC source; said three passive electrical branches comprise a first branch consisting of a capacitor, a second branch consisting of a reactor, and a third branch consisting of a resistor; and said completely-passive parallel resonant circuit being electrically connected to the neutral wire of the wye-portion of said delta-wye transformer.